Repeated peripheral stem cell mobilization in healthy donors: time-dependent changes in mobilization efficiency.

Mobilization of peripheral blood stem cells was analysed in 10 consecutive healthy donors undergoing repeated stem cell mobilization for allogeneic transplantation. Donors received recombinant G-CSF at a dose of 10 microg/kg/d for both mobilizations. Collection of stem cells was started on day 5 of G-CSF administration. To compare the efficiency of first and second mobilization, we determined the leucocyte and CD34+ cell counts in peripheral blood, and the yield of nucleated cells and CD34+ cell counts in the apheresis product. CD34+ cell numbers in peripheral blood were (median) 81.2 x 10(6)/l during the first and 50.4 x 10(6)/l during the second mobilization (P = 0.007). Likewise, CD34+ cells in the apheresis product decreased from 319.8 x 10(6) to 275.7 x 10(6) (P = 0.02). Decrease in CD34+ cell counts in peripheral blood and in the apheresis product was associated with the time interval between first and second mobilization. In a regression analysis there was a correlation between the ratios of CD34+ cell counts of first and second mobilization and the inverse of time interval between procedures (r2 = 0.51 peripheral blood; r2 = 0.74 apheresis product). Thus, stem cell yield is reduced when healthy donors receive repeated mobilization within a short time. Nevertheless, an adequate number of stem cells may repeatedly be mobilized within 2 months.